The P,M,and K streams in the primate visual system(Kaplan,2008) Property P M K 1 Clear spectral opponency Yes(red-green) No Some(blue-yellow) 2 Response to light steps Tonic Phasic (transient) Phasic;some sluggish 3 Luminance contrast gain Low High Diverse(some high) 4 Receptive field size Small Large Large 5 Spatial resolution of individual Similar to M Similar to P Diverse(some like M) neurons 6 Retinal ganglion cell density (acuity High Low ? of cell group) 7 Retinal source Midget RGCs Parasol RGCs Unknown(some blue-ON bistratified RGCs) 8 LGN projection target Parvocellular Magnocellular Koniocellular (intercalated) layers 9 V1 projection target Layer 4CB Layer 4Ca Layers 2-3,CO blobs,layer 1 10 Cell body size Small Large Large/varied 11 Conduction velocity of retinal Medium High Low/varied axons 12 Contrast sensitivity at scotopic Poor Good ? luminance 13 Linearity of spatial summation Linear (X-like) 75%Linear,25% Linear (X-like) Nonlinear(Y-like) 14 Extraclassical receptive field Weak Strong Intermediate (varied) effects 15 Number of cells (fraction of LGN ~1000000 70000(6%) 100000(9%) population) (85%)The P, M, and K streams in the primate visual system (Kaplan, 2008)